HELP PLEASE, I JUST HAD MY HAIR for the first time?

dyed about 2 weeks ago. my hair color is naturally brown. long story short, i HATE IT. ughh. i wanted two pretty light browns but i got dark brown with highlights, i didnt want highlights AT ALL. but my bros gf did it cuz shes a hair stylist and i didnt know she was highlighting my hair when she was doing it. but anyways she toned the highlights and now they are like yellow. UGLYYYYY. so i went to a consultation today at the salon i usually go to for my haircuts, and she said the only thing i could do would be to use a toner to tone the highlights, but my question is would the toner make the rest of my hair even darker too? or would the toner just target the highlights? she said i couldnt get light brown because she said i could only go darker NOT LIGHTER :(